Every diamond is different, incorporating a complex constellation of factors that determine the rarity of each stone. Although gemologists train for years to master the art and science of diamond appraisal, with a little basic instruction, anyone can learn how to read an appraisal and compare the grades of different stones.

Each diamond is as unique as the person who owns it. Just as a diamond reflects the color of the light it bears, it should also reflect the personality of the individual who wears it. Here lies the art of selecting a diamond, for yourself or as a gift.

Your knowledge of yourself, if you are buying for yourself, or your knowledge of a loved one, if the diamond is a gift, is expressed in your selection. Through your choice of a diamond, you are making a public statement about the loved one--and about your relationship--and that statement is repeated every time the diamond is worn.

This is why, for many women, there is such mystique in diamond jewelry gifts, and why, for many men, there is such uncertainty in its selection. What is important in the selection of a diamond has little to do with the cost of the jewelry and much to do with the richness of the relationship.

Truly flawless diamonds are very rare, and very expensive, so you will seldom face the task of selecting a perfect diamond. It is a fairly simple matter to find beautiful diamonds with no flaws visible to the naked eye and buy them at reasonable prices.

Diamonds are graded using a system that judges the stone on its color, clarity, cut and carat weight - commonly known as the "four C's." Diamonds of uncommonly high quality and size are often sold as "certified diamonds" and come with a certificate that proves the stone's value. Even non-certified diamonds, however, should be evaluated using the four C's to help determine cost.

Here you will learn what each of the C's means and how it affects the value of the diamond. Although it takes a trained eye to actually see the qualities described here, knowing what they mean can help you make a good choice in selecting your diamond.

Diamond Color

Most diamonds appear colorless but actually have slight tones of yellow or brown. The closer the stone comes to colorless, the more valuable it is. Diamonds are graded on a color scale ranging from D (colorless) to Z (heavily tinted.) Only a highly skilled professional will detect any color in E or F stones, and the color in diamonds rated up to J will be virtually invisible when set in a ring or other jewelry.

Color is only one of the four C's so even when a stone has a visible tint, such as K or above, it can still be very lovely if it has good clarity and cut. How the diamond is set can make a difference, too; you might not want to put a truly colorless diamond in a yellow gold setting since the yellow color will reflect in the stone. On the other hand, a slightly yellow stone will appear whiter in a yellow gold setting.

Diamonds also come in a wide variety of other colors, including red, blue, green and a bright yellow known as "canary." These are graded as Z+ and are known as "fancy" diamonds. Ones with good color are very rare and can sell for much more per carat than white diamonds.

Diamond Clarity

It is very common for diamonds to be formed with slight imperfections. These are known as "inclusions" and can come in many forms, including tiny white points, dark dots, or feathery cracks. The fewer inclusions, the more the stone is worth. A diamond's clarity ranking is determined by the number, size, type and placement of the inclusions.

A stone with only a few hard-to-see pinpricks located near the edge, where they can be covered by the mounting, has better clarity than a stone with a crack located right under the table (the large top facet of the stone). Cracks from the surface to the interior are especially dangerous because the diamond could break if hit the wrong way. On the other hand, small nicks and chips on the surface are often of little concern because they can be polished away.

For the most part, diamonds used in jewelry are clean to the naked eye. In a certified diamond, the cracks are charted on the certificate and act as a fingerprint for identifying a particular stone.

Diamond Cut

In the strictest definition of the term, "cut" is not the same thing as "shape" - for example, the most popular cut for a diamond is the round brilliant cut, but there are also round Swiss cuts, round Old European cuts, and round 144-facet cuts. For the most part, however, the terms are used interchangeably, including on this site.

The 58-facet round brilliant cut is the most popular because of its fire and brilliance. (These terms describe the intensity of the color and brightness of the light one sees in a diamond.) This is achieved by cutting the stone to very exacting mathematically-determined proportions so as much light as possible is reflected out the top of the diamond.

The cut of a diamond refers not only to the shape of the diamond and number of facets, but also to the quality of the cut. A diamond with uneven or poorly proportioned facets won't be given the same grade of cut as an ideally proportioned and masterfully cut stone. This information will be found on the certificate of a certified diamond.

Diamond Carat

Carat is the term used to describe the weight of any gemstone, including diamonds. Although the definition of a carat has changed over time, since 1913 the international standard has been 200 milligrams, or 1/5 of a gram. Often, jewelers describe carats in 1/4 increments.

In jewelry pieces with more than one diamond, the carats may be described in terms of total carat weight (TW). This is the combined total weight of all the stones in the piece.

Diamonds can range in size from a fraction of a carat to several carats. Given the rarity of large stones, however, the price increases rapidly with size; therefore, a single 2-carat diamond will cost much more than two 1-carat diamonds. Very large diamonds with good color and clarity are very rare.

Expect to pay a premium for stones that are above a full carat weight. For example, a .95 carat diamond will cost a bit more than a .90 carat stone, but a 1-carat stone will cost significantly more than a .95 carat stone.